Texas Instruments SN74CBT3245APWRG4

Overview

SN74CBT3245APWRG4 from Texas Instruments is an octal FET bus switch IC designed for high-speed TTL-compatible bidirectional data routing between two 8-bit ports (A and B). It features a typical on-state resistance of 5 Ω, propagation delay as low as 0.25 ns at 5 V, and operates across −40°C to 85°C with supply voltage from 4 V to 5.5 V. It is used in address/data bus isolation, hot-swap interface buffering, and level-translating I/O expansion.

For engineers reviewing the SN74CBT3245APWRG4 datasheet, SN74CBT3245APWRG4 pinout, SN74CBT3245APWRG4 application, or SN74CBT3245APWRG4 equivalent, key selection criteria include its 5-Ω switch R_ON, 0.25-ns t_pd at 5 V, standard '245-type pinout compatibility, and OE-controlled high-impedance isolation between A/B ports.

Technical Context

The SN74CBT3245APWRG4 implements eight independent analog FET switches in a single 20-pin TSSOP package, each connecting corresponding A_n and B_n terminals. Its operation is controlled solely by a single active-low output-enable (OE) input: OE = low enables bidirectional conduction; OE = high places both ports in high-Z state.

No internal logic or level-shifting circuitry is present - it functions purely as a passive, voltage-controlled resistive path. The device requires no external biasing beyond V_CC and GND, and OE must be pulled up to V_CC via an external resistor during power-up/down to guarantee default high-Z behavior.

Key Specifications

Pinout & Package

TSSOP-20 (PW) package: 6.5 mm × 4.4 mm, 0.65 mm pitch, 2.0 mm max height, exposed thermal pad not present. Pin 1 index located at top-left corner with notch or dot marking.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal bus switch applications.

Compared with SN74CBT3245APWRG4, SN74CBTD3384PWR adds level-shifting capability at the cost of higher R_ON and supply complexity, while 74LVC245APW offers direction control but lacks true analog pass-gate behavior and sub-nanosecond timing - making SN74CBT3245APWRG4 optimal for low-latency, bidirectional, voltage-transparent bus gating.

Availability

SN74CBT3245APWRG4 is available at Aetrix Electronics and suitable for industrial automation interfaces, telecom line-card bus isolation, and embedded test equipment requiring stable component supply over extended production lifecycles.

Supply support for SN74CBT3245APWRG4 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and communications markets.

The SN74CBT3245APWRG4 belongs to TI's CBT (CrossBar Technology) family of high-speed FET bus switches, engineered specifically for low-latency, low-R_ON, bidirectional signal routing in 5-V digital systems without introducing logic delay or voltage translation.

FAQ

What is the maximum continuous current rating per channel for the SN74CBT3245APWRG4?

The SN74CBT3245APWRG4 supports a continuous channel current of 128 mA per switch. This rating is specified under absolute maximum conditions and assumes proper thermal management. In typical operation at 25°C ambient with 5 V supply, each channel safely handles ≥64 mA with ≤0.32 V drop (based on 5 Ω R_ON). Derating is required above 70°C ambient per TI's thermal guidelines.

Does the SN74CBT3245APWRG4 require external pull-up resistors on the OE pin?

Yes - to ensure high-impedance state during power-up or power-down, OE must be tied to V_CC through an external pull-up resistor. TI recommends a value ≤10 kΩ for standard 5-V systems, sized to sink <1 mA while exceeding the input leakage current (±5 μA). Failure to implement this risks unintended conduction during supply ramping.

Can the SN74CBT3245APWRG4 be used for bidirectional level translation between 3.3-V and 5-V logic?

The SN74CBT3245APWRG4 supports voltage translation only in the sense that either port may operate up to 5.5 V, but it does not provide active level shifting. When used between 3.3-V and 5-V domains, signals pass through with minimal attenuation, provided both sides share a common ground and voltage levels remain within the device's absolute maximum ratings (−0.5 V to 7 V). For strict rail-to-rail translation, SN74CBTD3384PWR is recommended instead.

What is the thermal resistance (θ_JA) of the SN74CBT3245APWRG4 in its TSSOP-20 (PW) package?

The SN74CBT3245APWRG4 in the PW package has a junction-to-ambient thermal resistance (θ_JA) of 83°C/W, measured per JESD 51-7 on a standard 4-layer JEDEC test board. This value assumes 1 in² copper area per side under the package. Actual θ_JA in end equipment will vary based on PCB layout, copper pour, and airflow; design margin should include ≥20°C derating for reliable operation at full load.

Is the NC pin (Pin 20) on the SN74CBT3245APWRG4 internally connected or usable as a thermal pad?

No - Pin 20 is explicitly designated "NC" (no internal connection) in the SN74CBT3245APWRG4 datasheet and package drawings. It is not bonded to die or substrate and must remain unconnected. Unlike QFN packages, the TSSOP-20 (PW) variant has no exposed thermal pad; thermal dissipation relies solely on leads and PCB copper. Soldering Pin 20 provides no benefit and risks shorting adjacent traces.